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Questions and Answers
What must HCO3− react with before it can be reabsorbed?
Which process is involved in the secretion of H+ in the kidneys?
What is the pH of the tubular fluid considered maximally acidic?
What occurs as H+ is secreted in excess of the filtered HCO3−?
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What is the role of the phosphate buffer system in the kidneys?
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For each bicarbonate (HCO3−) reabsorbed, what must happen?
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What mechanism contributes to forming ‘new’ HCO3− during H+ secretion?
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Which transport mechanism is NOT involved in HCO3− reabsorption?
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What is the primary way kidneys regulate acid-base balance regarding bicarbonate?
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How much bicarbonate is typically filtered by the kidneys in a day?
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Why cannot bicarbonate ions be directly reabsorbed in the renal tubules?
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Which of the following processes helps rid the body of non-volatile acids?
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What is the role of De Novo synthesis in renal acid-base regulation?
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What is the estimated daily excretion amount of hydrogen ions?
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What takes precedence in the renal handling of bicarbonate ions?
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What is the approximate amount of bicarbonate reabsorbed by the kidneys daily?
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What happens to H+ secretion during acidosis?
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How do kidneys respond to chronic acidosis?
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What characterizes respiratory causes of acid-base disturbances?
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What is the renal response during alkalosis?
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What mechanism occurs when there is a reduction in plasma HCO3- concentration?
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What is a direct effect of increased ventilation rate on acid-base balance?
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What is the Henderson-Hasselbalch equation used for in acid-base balance?
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Which statement is true about bicarbonate management in the kidneys during acidosis?
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What is the net effect when H+ secreted into the tubular lumen combines with a buffer other than HCO3-?
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Which buffering mechanism accounts for much of the buffering of excess H+ in tubular fluid during acidosis?
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In chronic acidosis, what is the dominant mechanism for acid elimination?
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What does an increased anion gap indicate in the context of metabolic acidosis?
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What is the primary source of glutamine involved in NH4+ production?
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What are considered unmeasured cations in the ionic balance equation?
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What happens to the filtered phosphate under normal conditions?
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How are pH and PCO2 changes related in respiratory acid-base disorders?
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Which statement accurately reflects the role of buffers in the nephron?
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During the acidosis process, which buffering system predominantly facilitates bicarbonate absorption into the blood?
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What is considered a normal range for the anion gap (AG)?
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How does the body respond to chronic acidosis concerning NH4+?
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Which of the following would NOT contribute to an increased anion gap?
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What is the relationship between pH and PCO2 in metabolic acid-base disorders?
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Which of the following components are included as unmeasured anions in the ionic balance equation?
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What condition correlates with an anion gap greater than 20 mEq/L?
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Study Notes
Renal Regulation of Acid-Base Balance
- Bicarbonate (HCO3-) is filtered (~4320 mEq/day), reabsorbed (~4319 mEq/day), and secreted (H+ ~4400 mEq/day).
- HCO3- cannot permeate luminal membranes and must react with secreted H+ to form carbonic acid (H2CO3) for reabsorption.
- Each reabsorbed HCO3- requires an H+ to be secreted, crucial for maintaining acidic urine (pH of tubular fluid ~4.5).
Mechanisms of Secretion and Reabsorption
- Secondary Active Transport involves Na+-H+ counter-transport for HCO3- reabsorption, while primary active transport uses H+-ATPase for H+ secretion.
- Buffering mechanisms include phosphate buffers (NaHPO4-) and ammonia (NH3), which helps remove excess H+ and generates new HCO3-.
Urinary Buffering
- Phosphate buffers H+ in the tubular fluid when H+ exceeds filtered HCO3-, generating new bicarbonate.
- Only 30-40 mEq/day of filtered phosphate is available for buffering; ammonia becomes predominant in chronic acidosis.
Acid-Base Disturbances
- Acidosis: Increased H+ secretion and excretion, enhanced HCO3- reabsorption, and new HCO3- production.
- Alkalosis: Decreased H+ secretion and excretion, decreased HCO3- reabsorption leading to HCO3- excretion in urine.
Diagnosis and Compensation of Acid-Base Disorders
- Acid-Base Nomogram helps visualize normal compensation limits for metabolic and respiratory disorders.
- In respiratory issues, pH and PCO2 change in opposite directions; in metabolic disorders, they change in the same direction.
Anion Gap and Its Significance
- Anion gap (AG) is calculated as [Na+] - ([Cl-] + [HCO3-]), normal values range from 10-14 mEq/L (average 12 mEq/L).
- An increased AG (>20 mEq/L) suggests metabolic acidosis, often due to increased unmeasured anions or decreased unmeasured cations.
Clinical Applications
- AG assists in differentiating causes of metabolic acidosis, indicating conditions like hyperalbuminemia, lactic acidosis, or ketoacidosis.
- Understanding these mechanisms is vital for diagnosing and managing acid-base disturbances in patients.
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Description
This quiz explores the mechanisms of renal regulation of acid-base balance. It covers key concepts related to how the kidneys maintain proper pH levels and manage absorption processes. Test your understanding of these vital physiological functions.
